JP3064919B2 - Noise prevention method and circuit for sensitivity inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a circuit for preventing mixed noise in a reception sensitivity inspection apparatus for detecting the sensitivity of the sound of a pager receiver, and more particularly to an analog reception sensitivity inspection apparatus.

[0002]

2. Description of the Related Art An example of a conventional general sensitivity inspection apparatus is shown in FIG.
This is shown in the configuration diagram of FIG.

[0003] This sensitivity inspection apparatus includes a shield box 41 in which a pager receiver 47 is installed, a microphone 42 installed in the shield box 41, and a microphone 42.
, An amplifier 43 connected to the output of the amplifier 43, a bandpass filter 44 connected to the output of the amplifier 43, a comparator 45 connected to the output of the bandpass filter 44, and a trigger input terminal connected to the output of the comparator 45. It includes a latch circuit 46 and a control unit 48 connected to the output of the latch circuit 46.

Next, the operation of the sensitivity inspection apparatus will be described.

When the pager receiver 47 makes a sound, the microphone 42 converts the input sound wave into an electric signal aa and outputs it to the amplifier 43. The amplifier 43 amplifies the electric signal aa and outputs it to the band-pass filter 44 as an electric signal bb. The band-pass filter 44 passes only the sound frequency component of the pager receiver 47 out of the components of the electric signal bb and outputs it to the comparator 45 as the electric signal cc. The comparator 45 compares the electric signal cc with the threshold level and outputs the same to the latch circuit 46 as a square wave electric signal dd. The latch circuit 46 performs a latch operation based on the waveform edge of the electric signal dd, and outputs the electric signal ee to the control unit 48. The control unit 48 detects the sensitivity of the sound of the pager receiver 47 based on the electric signal ee.

However, in the above-described conventional sensitivity inspection apparatus, since the microphone is fixed to the shield box, if a shock or vibration is applied to the shield box during the inspection, the microphone also generates noise due to the shock or vibration. There is a problem that the signal is converted into an electric signal, the control unit cannot distinguish it from the sound of the pager receiver, and erroneous detection occurs.

The applicant of the present application has previously filed a Japanese Patent Application No. 4-9616 (Japanese Patent Application Laid-Open No. Hei 5-218938) for a sensitivity inspection apparatus which solves this problem. The sensitivity inspection apparatus of this application focuses on the difference in continuous time between the sound of the pager receiver and the sound due to shock or vibration, and as shown in FIG. The non-retriggerable mono-multivibrator 56 having a pulse width longer than the pulse generation time caused by the above-mentioned method is introduced, and the edge of the output of the comparator 55 is latched by the latch circuit 57 when the output of the mono-multivibrator 56 is disabled. Is distinguished from the sound of the pager receiver to enhance the accuracy of the sensitivity test.

In general, since the continuous time of the sound due to shock or vibration which is an obstacle to the inspection is shorter than the continuous time of the sound of the pager receiver, the length of the output signal ee of the mono-multivibrator 56 represented by the number of pulses is reduced. , Detection signal d due to impact
If it is set longer than the generation time of d ′, the pulse of the output signal dd of the comparator 55 is output to the trigger input terminal of the latch circuit only while the signal ee input to the clear signal input terminal of the latch circuit 57 is enabled. Circuit 5
7 is disabled and the control unit 5
8 is prevented from being erroneously detected.

[0009]

Problems to be Solved by the Invention Japanese Patent Application No. 4-96 mentioned above.
Although the sensitivity inspection device according to No. 16 is effective in preventing mixed noise, the sound detected by the microphone is processed in a digital system, so the present invention improves this to an analog system to further improve the inspection range. And to provide a sensitivity inspection apparatus capable of performing a highly accurate sensitivity inspection.

[0010]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for preventing noise in a sensitivity test apparatus, comprising the steps of: amplifying and rectifying an analog electric signal converted from a sound; Compare the voltage of the reference power supply of 1 and charge the capacitor with a positive voltage when the voltage of the rectified electric signal is larger and a negative voltage when the voltage of the rectified electric signal is smaller. Controls the inspection output signal.

The predetermined value of the charging voltage of this capacitor is:
It is preferable to set the charging time of the capacitor to be shorter than the sounding duration of the pager receiver and longer than the expected duration of the mixed noise.

The noise prevention circuit of the sensitivity inspection apparatus to which the present invention is applied has a rectification means for rectifying the output current of the amplifier, wherein the noise prevention means outputs the output of the rectification means to the voltage of the first reference power supply. A first comparing means for comparing the voltage of the first comparing means with the voltage of the second reference power supply, and an output means for comparing the voltage of the capacitor means with the voltage of the second reference power supply and outputting the result.

According to the noise prevention circuit of the present invention , the rectifier has a diode bridge for full-wave rectifying the output of the amplifier, a resistor for converting the output current of the diode bridge into a voltage, and an output of the resistor connected in parallel with the resistor. A first capacitor for smoothing the peak of the pulsating waveform of the voltage, and a first comparing means, the output of the smoothed diode bridge and the first capacitor.
Compares the reference power, a positive voltage signal when the output of the diode bridge is large, greater first reference power source comprises a first comparator for outputting a negative voltage signal, the output control means, said It comprises a second comparator which inputs the output of the second capacitor charged by the output of the first comparator and the second reference power source, compares them, and outputs the result.

The capacitor means includes a first and a second output circuit for outputting the output of the first comparator by a voltage follower.
Two buffer amplifiers, a second capacitor for charging the output voltage of the second buffer amplifier, and one contact end connected to the output terminal of the second buffer amplifier via the second capacitor, It is preferable that an end of the contact is connected to the ground potential, and a switch whose opening and closing are controlled by an output of the first buffer amplifier is included.

[0015]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a first embodiment of the present invention, and FIG.
Is a signal waveform diagram of the input b of the diode bridge 4 and the outputs f and h of the comparator 8 and the comparator 11,
(A) is a waveform diagram when the pager receiver 12 sounds, and (B) is a waveform diagram when an impact or vibration is applied to the shield box 1.

In FIG. 1, a sensitivity inspection apparatus according to a first embodiment includes a shield box 1 in which a pager receiver 12 is installed, an amplifier 3 connected to a microphone 2 installed in the shield box 1, A diode bridge 4 connected to the amplifier 3, a parallel circuit of a resistor 5 and a capacitor 6 connected to the output of the diode bridge 4, an output of the diode bridge 4 output through a parallel circuit of the resistor 5 and the capacitor 6, and A comparator 8 for comparing the first reference power supply 7, a capacitor 9 inserted between an output terminal of the comparator 8 and the ground potential and charged by an output of the comparator 8, a second reference power supply 10 and an output of the comparator 8 And a comparator 11 for comparing and outputting.

Next, the operation of the first embodiment will be described. When the pager receiver 1 sounds, the microphone 2 converts the sound wave into an electric signal a and outputs the electric signal a to the amplifier 3. Amplifier 3 amplifies electric signal a and outputs electric signal b to diode bridge 4. The diode bridge 4 performs full-wave rectification of the electric signal b and outputs the electric signal b to the comparator 8 as an electric signal d via a parallel circuit of a resistor 5 and a capacitor 6. The comparator 8 compares the electric signal e output from the reference power supply 7 with the electric signal d. If the electric signal d is larger than the electric signal e, the comparator 8 outputs the positive voltage electric signal f and the electric signal d. Is smaller, a negative voltage electric signal f is output. The voltage input to the comparator 11 is controlled by charging the capacitor 9 when the electric signal f is a positive voltage and discharging the capacitor 9 when the electric signal f is a negative voltage. The comparator 11 compares the input electric signal f with the electric signal g of the reference power supply 10, and outputs the electric signal h as a positive voltage when the electric signal f is larger, and outputs the electric signal h with a positive voltage when the electric signal f is smaller. Output the electric signal h as a negative voltage.

FIG. 2A shows an example of a waveform of an electric signal when a sound of the pager receiver 12 to be inspected is inputted. The electric signal b input from the amplifier 3 to the diode bridge 4, the comparator, 8 shows the waveform of the electric signal f charged from the capacitor 8 to the capacitor 9 and the electric signal h of the output of the comparator 11, and FIG. 2B shows the electric signal b 'at the same location when the shield box 1 is shocked. , F ′, h ′.

The length of the waveform of the electric signal b ′ due to the impact is
It is shorter than the length of the waveform of the electric signal b due to the sound of the pager receiver. The voltage charged in the capacitor 9 gradually increases during the sounding as shown by the waveforms f and f ′, but decreases when the sounding stops, with the reached voltage value being the highest value. Therefore, by adjusting the capacity of the capacitor 9 and the voltage of the electric signal g of the reference power supply 10, the electric signal g of the reference power supply 10 is adjusted.
Is larger than the maximum value of the waveform f ′ due to an impact or the like,
When the value is smaller than the maximum value of the waveform f due to the sound of the pager receiver 12, the sound due to an impact or the like is removed, and only the sound of the pager receiver 12 can be detected.

Next, a second embodiment of the present invention will be described.

FIG. 3 is a block diagram of a second embodiment of the present invention.

In the second embodiment, buffer amplifiers 13 and 14 and switches 15 are added to the circuit of the capacitor 9 in the first embodiment.
Is added.

That is, the output signal f of the positive or negative comparator 8, which is the result of comparison between the output e of the reference power supply 7 and the output signal d of the diode bridge 4, is supplied to the buffer amplifier 1
3 and the buffer amplifier 14. The buffer amplifier 14 converts the signal j obtained by voltage-following the signal f into the capacitor 9, one contact of the switch 15, and the comparator 1
Output to 1. On the other hand, the buffer amplifier 13 applies a voltage follower to the signal f and outputs an electric signal i to the switch 15. The switch 15 opens the contact when the signal i is a positive voltage, closes the contact when the signal i is a negative voltage, grounds the capacitor 9,
Is set to 0.

Therefore, the capacitor 9 is charged when the signal j has a positive voltage, and discharged when the signal j has a negative voltage, so that the voltage of the signal j is controlled.

The comparator 11 compares the input signal j with the signal g of the reference power supply 10, and outputs a positive signal when the signal j is larger, and outputs an output signal h when the signal j is smaller. The signal h is output as a negative voltage.

By accelerating the discharge of the capacitor 9 in this manner, even when an impact or the like is intermittently applied repeatedly, the influence of the impact can be removed and the sound for measurement can be correctly detected.

[0028]

As described above, the present invention provides a diode bridge.
Conversion means consisting of a resistor, a resistor and a first capacitor
And a first comparing the output of the conversion means with the first reference power supply.
Comparing means, the output of the first comparing means and the second reference power supply.
Output control means for outputting the comparison result, and the conversion means
When the stored input voltage value is higher than the first reference power supply voltage
Output a detection signal to reduce the
Can be removed to detect only the sound of the pager receiver.
Therefore, there is an effect that it is possible to provide a simple circuit that prevents noise input other than the sound of the pager receiver to be measured and increases the accuracy of the sensitivity inspection device of the pager receiver.

Further, the noise prevention means includes first and second two.
One buffer amplifier and a second buffer amplifier.
A second capacitor to be charged and a first buffer amplifier.
Output of the detection signal by the output of the second buffer
Switch that switches to either the output of the
To accelerate the discharge of the second capacitor.
When the impact is intermittent and repeated,
By removing the effect, the sound for measurement can be detected correctly.
Wear.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a first embodiment of the present invention.

FIG. 2 is a signal waveform diagram of an input “b” of a diode bridge 4 and outputs “f” and “h” of a comparator 8 and a comparator 11, wherein (A) is a sound of the pager receiver 12 and (B) is an impact on the shield box 1; FIG. 6 is a waveform diagram when vibration is applied.

FIG. 3 is a circuit configuration diagram of a second embodiment of the present invention.

FIG. 4 is a circuit configuration diagram of an example of a conventional sensitivity inspection device.

FIG. 5 is a circuit configuration diagram of another example of a conventional sensitivity inspection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shield box 2 Microphone 3 Amplifier 4 Diode bridge 5 Resistance 6 Capacitor 7 First reference power supply 8 Comparator 9 Capacitor 10 Second reference power supply 11 Comparator 12 Pager receiver to be inspected 13, 14 Buffer amplifier 15 Switch

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B 17/00 H04B 7/26 H04Q 7/14

Claims (2)

(57) [Claims] 1. An external electric field is cut off and a pager is internally received.
And a shield box for storing the pager, and the pager receiver
A microphone that inputs the sound produced by and converts it into an electrical signal,
Amplifier for amplifying an electric signal output from the microphone
Converting means for converting the output current of the amplifier into a voltage
To prevent noise other than the sound of the pager receiver.
Noise converting means, and the converting means comprises:
A rectifier for rectifying an output current of the amplifier;
Preventing means for outputting the output of the converting means to a power supply of a first reference power supply;
First comparing means for comparing the pressure with the pressure, and the output of the first comparing means.
Capacitor means charged by force, and said capacitor
Test output by comparing the voltage of the means with the voltage of the second reference power supply
Of a sensitivity inspection apparatus having output control means for controlling a signal.
In the noise prevention circuit, the conversion unit includes a diode bridge that performs full-wave rectification on the output of the amplifier, a resistor that converts an output current of the diode bridge into a voltage, and an output voltage of the resistor that is connected in parallel with the resistor. A first capacitor for smoothing the peak of the pulsation waveform, wherein the first comparing means inputs the output of the converting means and the first reference power supply and compares them, and the output of the converting means is large. A first comparator that outputs a signal of a positive voltage if the first reference power supply is large, and a first comparator that outputs a signal of a negative voltage if the first reference power supply is large, and an output control means of the second capacitor charged by the output of the first comparator. A noise prevention circuit for a sensitivity inspection device, comprising: a second comparator that inputs an output and a second reference power supply, compares the two, and outputs the result . 2. The method according to claim 1, wherein the capacitor means of the noise prevention means comprises :
First and second two buffer amplifiers that output the output of the comparator of the first and second comparators with a voltage follower, and a second capacitor that charges the output voltage of the second buffer amplifier.
One contact end is connected to the output terminal of the second buffer amplifier via the second capacitor, and the other contact end is connected to the ground potential. The noise prevention circuit according to claim 1 , further comprising: a switch that controls opening and closing of a contact.